What Is ALERT?

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ALERT systems are used around the world to provide real-time flood warning to local communities at risk from flooding threat.

An ALERT system is characterized by its real-time nature, accomplished by the instantaneous transmission of weather events primarily by radio transmission, and to a lesser extent by satellite, telephone, and cell phone transmission. Changes in rainfall, stream, weather and lake levels throughout San Diego County are transmitted by radio to mountaintop repeaters, which in turn relay the transmission to our District Flood Warning office in Kearny Mesa. In Kearny Mesa, the radio signals are intercepted and also relayed by independent radio repeaters to the National Weather Service (NWS) in San Diego. This data is received by ALERT computers which check the data for validity, check against established warning criteria for that data, update any displayed maps, then place the data into a database. If any warning criteria are met, the computers will put out a visible, audible, and/or pager warning.

In San Diego County, a partnership has evolved between the Flood Control District (FCD), the NWS, and the County Office of Emergency Services (OES). The FCD is responsible for the maintenance and operation of the ALERT Flood Warning System. When flooding conditions develop, the FCD evaluates the flooding potential presented by the ALERT data and advises the NWS and OES on possible flooding in the County. The NWS will complete the assessment of flooding potential using their resources and will issue a forecast update, special weather statement, flash flood watch, or flash flood warning. OES will pass along the NWS warnings and watches to relevant agencies within San Diego County and will coordinate Disaster Relief Operations whenever necessary.

Because of its nature, the ALERT system can monitor anything that provides a contact closure, a voltage range of 0-5 volts, or a current range of 4-20 mA. This makes it ideal not only to provide real-time flood warning, but can also monitor water resource parameters such as: winds, temperature, humidity, barometric pressure, groundwater levels, soil moisture, fuel moisture, water temperature, water quality, and evaporation. ALERT field transmitters with control capability can also perform physical functions such as activating low water crossing flood warning gates and signals, raising flood control barriers, or setting off warning sirens.

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